JP2000187468A - Picture display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a picture display device which is of low power consumption and capable of preventing pseudo colors and coloring at edge parts. SOLUTION: This is a picture display device provided with a picture signal processing means 11 for processing a picture signal, a picture signal output means 11 for separating the processed picture signal into those of red, green, and blue and outputting them in time-division manner, a liquid crystal display unit 7 wherein all the picture elements can transmit red, green, and blue light and the unit varies the transmissivity of each picture element according to the red, green, and blue picture signals outputted from the picture signal output means, red, green and blue light emitting diodes 10 capable of irradiating the back of the liquid crystal unit with these lights, and a light emitting diode control means 11 for making the red, green, and blue diodes emit light correspondingly to the timing when the picture signal output means outputs the red, green, and blue picture signals.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an image display device, and more particularly to an image display device having a liquid crystal display and a light emitting diode.

[0002]

2. Description of the Related Art Liquid crystal display devices include a backlight type and a reflection type. In the backlight type, the liquid crystal surface is illuminated from behind with a fluorescent lamp (backlight) to display. The reflection type does not have a fluorescent lamp and displays by utilizing reflection of external light.

[0003]

The backlight type is easy to see in a dark place such as indoors, but difficult to see in a bright place such as outdoors. Conversely, the reflection type is easy to see in a bright place such as outdoors, but difficult to see in a dark place such as indoors. In both cases, the visibility of the display depends on the surrounding brightness.

[0004] In the backlight type, since the power consumption of the fluorescent lamp inside is large, when the liquid crystal display device is driven by a battery, the continuous operable time (battery life) of the liquid crystal display device is relatively short. .

In a color liquid crystal display device, a color filter is provided in a portion corresponding to each pixel on a liquid crystal surface. Since the color filter transmits only the wavelength of a predetermined color component, light use efficiency is poor.

In a color liquid crystal display device, color filters are arranged, for example, in a delta arrangement, and a color filter of a different color is provided for each pixel on the display surface. Each pixel on the display surface is 3
Since the image does not have a color, coloring or a false color occurs at an edge portion on the image, and the image quality is deteriorated.

An object of the present invention is to provide an image display device capable of preventing false colors and coloring at edge portions.

Another object of the present invention is to provide an image display device with low power consumption. Still another object of the present invention is to provide an image display device capable of satisfactorily viewing an image without being substantially affected by peripheral brightness.

[0009]

According to one aspect of the present invention, there is provided an image signal processing means for processing an image signal, and converting the image signal processed by the image signal processing means into red, green and blue image signals. Image signal output means for dividing and outputting in a time-sharing manner, and all the pixels are capable of transmitting red, green and blue light, and each pixel is transmitted in accordance with the red, green and blue image signals output by the image signal output means. A liquid crystal display that changes the transmittance of pixels, red, green, and blue light-emitting diodes that can illuminate the back surface of the liquid crystal display, and corresponding to the timing at which the image signal output means outputs a red image signal. The red light emitting diode emits light, and the image signal output unit emits the green light emitting diode corresponding to the timing of outputting the green image signal, and the image signal output unit emits the blue light. An image display device having a light-emitting diode control means so as to correspond to the timing of outputting the image signal to emit the blue light-emitting diode is provided.

In the liquid crystal display, all the pixels can transmit red, green and blue light, and the red, green and blue light emitting diodes illuminate the back of the liquid crystal display. It has a color component and can prevent false colors and coloring at an edge portion.

[0011] A light emitting diode illuminates the back of the liquid crystal display. Since a light emitting diode consumes less power than a fluorescent lamp, when the image display device is driven by a battery, the continuous operable time (battery life) of the image display device can be relatively long.

Without providing a color filter on the liquid crystal display,
Since coloring is performed by light emitting diodes of three colors, light use efficiency is high. In other words, power consumption for obtaining image signals of the same luminance can be reduced.

[0013]

FIG. 1A is a configuration diagram of an image display device according to an embodiment of the present invention.

The image display device 1 has a finder section 2 and a control circuit section 3. The finder section 2 is provided with a lens 5 which is a magnifying optical system. The user 4 looks into the viewfinder 2 through the lens 5. The finder section 2 sequentially blocks the lens 5, the polarizing plate 6, the liquid crystal display (LCD) 7, the polarizing plate 8, the diffusion plate 9, and the light emitting diode (LED) 10 from the outside in the line of sight of the user 4. To store.

The light emitting diode 10 has a red light emitting diode 10a, a green light emitting diode 10b, and a blue light emitting diode 10c, and emits light in response to a control signal SLED. The three light emitting diodes 10a, 10b, 10c
Either one selectively emits light in a pulsed manner in a time-division manner.
The light emitting diode 10 has a function as a backlight of the liquid crystal display 7 and a function of determining a display color of the liquid crystal display 7. Details will be described later with reference to FIG.

The diffusion plate 9 is made of plastic frosted glass and diffuses light emitted from the light emitting diode 10. The light emitting diode 10 is close to a point light source. The diffusion plate 9 diffuses the light of the light emitting diode 10, so that the light of the light emitting diode 10 can be uniformly applied to the entire rear surface of the liquid crystal display 7.

The liquid crystal display 7 has pixels arranged two-dimensionally, and the light transmittance of each pixel changes according to the image signal ILCD and the control signal SLCD. FIG. 1B is a cross-sectional view of the liquid crystal display 7. As shown in FIG. 1B, the liquid crystal display 7 includes a transparent substrate 21 having a pixel electrode 22,
It has a transparent substrate 25 having an entire surface electrode 24 and a liquid crystal layer 23 sandwiched between the transparent substrate 21 and the transparent substrate 25.
The liquid crystal display 7 has no color filter and can transmit red, green, and blue light in all pixels.

In accordance with the voltage applied between the electrodes 22 and 24, the transmittance of the liquid crystal layer 23 between the electrodes changes. The liquid crystal display 7 has a plurality of thin film transistors (TFTs) corresponding to the plurality of pixel electrodes 22, and one of the pixel electrodes 22 is selected by each thin film transistor. Each pixel electrode 22 corresponds to a pixel and is two-dimensionally arranged. Although only five pixel electrodes 22 are shown in the figure, the liquid crystal display 7 actually has, for example, 320 × 240 pixels. The liquid crystal display 7 may be a simple matrix type in addition to an active matrix type having thin film transistors.

In FIG. 1A, a liquid crystal display 7 is sandwiched between two polarizing plates 6 and 8. The polarizing plate 8 polarizes the light incident from the light emitting diode 10 via the diffusion plate 9 and emits the polarized light to the liquid crystal display 7. The liquid crystal display 7 transmits the light from the polarizing plate 8 at a predetermined transmittance for each pixel. The polarizing plate 6 detects light incident from the liquid crystal display 7 and emits the detected light to the lens 5.

The lens 5 is a magnifying lens, and a polarizing plate 6
, The image on the liquid crystal display 7 is optically enlarged. The finder section 2 prevents outside light from entering inside except for the lens 5 and also prevents light from the light emitting diode 10 from leaking from outside the lens 5.

By providing the finder unit 2 in the image display device 1, the user 4 approaches the lens 5 and looks into the finder unit 2. Since the image occupies most of the effective field of view of the user 4, the image can always be viewed satisfactorily without being affected by the surrounding brightness.

The control circuit section 3 has a power supply 13, a video source 12, and a control section 11. The power supply 13 is a power supply for driving the image display device 1, and is, for example, a 3V battery. The video source 12 is, for example, a solid-state imaging device or a flash memory, and includes a control command CMD, a synchronization signal CT,
L, and outputs the image signal DT to the control unit 11.

The control unit 11 receives signals CMD, CTL, DT
, The control signal SLED is output to the light emitting diode 10, and the image signal ILCD and the control signal SLCD are output to the liquid crystal display 7.

The video source 12 outputs a moving image or a still image. When the controller 11 detects that the image signal supplied from the video source 12 is a still image, the signal SL
P can be supplied to the video source 12 to stop the operation of all or a part of the video source 12, thereby reducing power consumption.

FIG. 2 is a timing chart showing the operation of the liquid crystal display 7 and the operation of the light emitting diode 10 described above. The image signal ILCD is a signal supplied to the liquid crystal display 7, and the control signal SLED is a signal supplied to the light emitting diode 10.

The red image signal 3 is used as the image signal ILCD.
1R, the green image signal 31G, and the blue image signal 31B are sequentially supplied to the liquid crystal display 7. Three color image signals 31R, 31
By combining G and 31B, a color image of one frame (one frame or one field) can be formed. When the image size of one frame is 320 × 240, each image signal 3
The sizes of 1R, 31G and 31B are also 320 × 240.

Each of the image signals 31R, 31G, 31B is supplied in raster scan order. That is, the pixels are arranged in the raster scan order from the pixel at the upper left corner to the pixel at the lower right corner of the image.
The liquid crystal display 7 maintains the alignment state of the liquid crystal until the liquid crystal acts as a capacitor and the next image signal is supplied.

The total time T1 of the three color image signals 31R, 31G and 31B is one cycle, which is 1/60 s.
That is, a color image of 60 frames / s can be obtained. The repetition pitch time T2 of the image signals 31R, 31G, and 31B of each color is 1/180 s (about 5.6 ms). The gap time (the time when there is no image signal) T3 between the image signals 31R, 31G and 31B of each color is about 1 ms.

As the light emitting diode control signal SLED,
The red control signal 32R, the green control signal 32G, and the blue control signal 32B are sequentially supplied as pulses to the light emitting diodes of each color. The control signal 32R is a signal for causing the red light emitting diode to emit light, and the control signal 32G is a signal for causing the green light emitting diode to emit light.
B is a signal for causing the blue light emitting diode to emit light.

First, a red control signal 32R is supplied after the red image signal 31R, and a red image is displayed on the liquid crystal display. Next, a green control signal 32G is supplied after the green image signal 31G, and a green image is displayed on the liquid crystal display. Next, after the blue image signal 31B, the blue control signal 32
B is supplied, and a blue image signal is displayed on the liquid crystal display.

Hereinafter, each or all of the image signals 31R, 31G, and 31B will be referred to as an image signal 31, and the control signals 32R,
Each or all of 32G and 32B is called a control signal 32.

The alignment of the liquid crystal of the liquid crystal display has a predetermined time delay. During a predetermined time after the supply of the image signal 31, the liquid crystal maintains its alignment state. Therefore, when the light emitting diode emits light, the liquid crystal maintains an alignment state corresponding to the image signal 31 of each color.

Also, since the human eye has an afterimage effect,
When a red image, a green image, and a blue image are repeatedly displayed in a time-division and high-speed manner, a human eye can see a color image in which three-color images are superimposed.

By supplying the control signal 32 after the image signal 31, the light emitting diode emits light in a pulsed manner after all the pixels of the liquid crystal display are controlled, and each color can be displayed. If the control signal 32 before the end of the image signal 31,
Is not preferable because it emits light before all the pixels of the liquid crystal display are controlled.

The high level time T4 of the control signal 32 indicating the light emission time of each light emitting diode is 0.5 ms to 2 ms. Each control signal 32 is preferably located in a gap between the image signals 31 of each color. However, the image signal 31
Since the majority of the liquid crystal pixels maintain the state of the previous color at the start of the image signal 31, the control signal 32 may be supplied at the start of the image signal 31.

A conventional color liquid crystal display device displays a color image of, for example, 60 frames / s. According to this embodiment, by supplying an image signal of each color of 180 frames / s, a color image of substantially 60 frames / s can be displayed, so that a relatively high quality image can be displayed. Can be.

Further, in the color liquid crystal display device according to the prior art, since the color filters are arranged in a delta arrangement, for example, and each pixel is one color, a false color or coloring at an edge portion occurs. In this embodiment, since all the pixels have three color signals, it is possible to prevent false colors and coloring at edge portions.

The backlight type liquid crystal display device according to the prior art has a fluorescent lamp for the backlight inside, but according to the present embodiment, has a light emitting diode instead of the fluorescent lamp. Since a light emitting diode consumes less power than a fluorescent lamp, when the image display device is driven by a battery, the continuous operable time (battery life) of the image display device can be relatively long.

In the color liquid crystal display device according to the prior art, a color filter is provided in a portion corresponding to each pixel on the liquid crystal surface, and the color filter transmits only a wavelength of a predetermined color component. bad. According to the present embodiment, since the coloring is performed by the three color light emitting diodes without providing the color filter in the liquid crystal display, the light use efficiency is high.

FIG. 3 is a flowchart showing the image signal processing in the control section 11 shown in FIG.

The control section 11 receives the signal from the video source 12 and controls the liquid crystal display 7 and the light emitting diode 10. The control unit 11 performs steps 41, 42, 43, 44
The processing is performed in this order. The order of steps 42, 43 and 44 may be interchanged.

In step 41, the image signal supplied from the video source 12 is stored in the frame memory. The rate of the image signal supplied from the video source 12 is free. The control unit 11 can input image signals of various rates from the video source 12. That is, the rate of the image signal is not limited to 60 frames / s. Further, the input image is not limited to a moving image, and may be a still image.

In step 42, the rate of the image signal is converted. Specifically, the image signal can be converted into a predetermined image signal rate by reading the image signal from the frame memory at a predetermined cycle. The rate of the converted color image signal is, for example, 30 to 100 frames / s, and is 60 frames / s.
s is preferred. That is, the rate of the image signal of each color is
It is 90 to 300 frames / s, preferably 180 frames / s.

In step 43, the R / G signal is converted from the Y / C signal.
/ B signal. The image signal can be expressed by a Y / C signal in addition to the R / G / B signal. Y /
The C signal is composed of a luminance (Y) signal and a chroma (C) signal.

If the image signal supplied from the video source 12 is a Y / C signal, the Y / C signal is converted into an R / G / B signal in step 43. If the image signal supplied from the video source 12 is an R / G / B signal, the conversion in step 43 need not be performed.

In step 44, gradation conversion of the image signal is performed. The transmittance of the liquid crystal display 7 changes according to the voltage. This transmittance corresponds to the gradation of the image. Liquid crystal display 7
In general, the voltage-transmittance characteristic does not match the gradation change of an image as seen by human eyes, so that gradation conversion of an image signal is performed using a look-up table (LUT). Details of the gradation conversion will be described later with reference to FIGS.

The control unit 11 controls the liquid crystal display 7 and the light emitting diode 10 based on the image signal on which the above processing has been performed. By the rate conversion in step 42, a color image can be displayed on the liquid crystal display 7 at a constant rate (for example, 60 frames / s). In step 43, the image signal is
The conversion to the G / B signal enables display on the liquid crystal display 7. By performing gradation conversion in step 44, gradation expression of an image that matches human visual characteristics becomes possible. Next, the details of the gradation conversion will be described.

FIGS. 4A and 4B are diagrams showing the gradation conversion in step 44 described above. FIG. 4A is a graph showing a voltage-transmittance characteristic of the liquid crystal display 7 in which gradation conversion is not performed. The horizontal axis is the voltage V applied to the liquid crystal display 7 corresponding to the gradation (pixel value), and the vertical axis is the transmittance T of the liquid crystal display 7.

The liquid crystal display 7 generally has either the characteristic line 45a or 45b. The characteristic line 45a has an upward convex shape in a low voltage region, and has a downward convex shape in a high voltage region. Conversely, the characteristic line 45b has a downward convex shape in the low voltage region, and has an upward convex shape in the high voltage region.

In both cases, the direction of the convex shape is different between the low-voltage region and the high-voltage region, so that they differ from human visual characteristics. When an image is displayed on the liquid crystal display 7 on the basis of the characteristic line 45a or 45b, a sense of incongruity is perceived by human eyes. Therefore, by performing gradation conversion, the image is adjusted to human visual characteristics.

FIG. 4B is a graph showing a voltage-transmittance characteristic of the liquid crystal display 7 which has performed gradation conversion. The horizontal axis is the voltage V of the image signal corresponding to the gradation (pixel value), and the vertical axis is the transmittance T of the liquid crystal display 7.

The liquid crystal display 7 has, for example, characteristic lines 46a,
6b or 46c. Characteristic lines 46a, 4
Any one of 6b and 46c may be selected. The characteristic line 46a has an upward convex shape in the entire voltage range, the characteristic line 46b has a linear characteristic,
c has a downward convex shape in the entire voltage region.

The gradation conversion is actually performed by converting the gradation (pixel value) corresponding to the voltage V on the horizontal axis. For example, when the image signal is 8 bits, the pixel value of each color can be expressed by 256 gradations. The pixel values before conversion and the pixel values after conversion are recorded in a lookup table in association with each other,
The conversion of the pixel value is performed using the lookup table. Next, the converted pixel value is converted into an analog voltage by a D / A converter. By applying the analog voltage to the liquid crystal display 7, the transmittance T of each pixel of the liquid crystal display 7 can be controlled.

FIG. 5 is a block diagram showing the internal configuration of the control unit 11 shown in FIG. The control unit 11 can be constituted by one IC.

The control unit 11 includes a command decoder 51, a drive signal generation unit 52, a memory control unit 53, and an input switch 5.
4, two buffer memories (frame memories) 55a,
55b, an output switch 56, an image signal processing unit 57, and a look-up table 58.

The image signal DT is alternately written into one of the buffer memories 55a and 55b via the input switch 54 in frame units. For example, the first frame is written into the buffer memory 55a, the second frame is written into the buffer memory 55b, the third frame is written into the buffer memory 55a, and the fourth frame is written into the buffer memory 55a.
5b. Buffer memories 55a and 55b
Are two frame memories, DRAM or SRA
M.

The switching of the input switch 54 is performed by the memory control unit 53. The memory control unit 53 includes a synchronization signal CTL
, The switches 54 and 56 and the buffer memory 55
a and 55b are controlled.

The synchronization signal CTL includes a clock signal CLK, a horizontal synchronization signal Hsync, and a vertical synchronization signal Vsync. The clock signal CLK is a basic clock for operating the control unit 11. The vertical synchronization signal Vsync is
The start timing of each frame of the image is shown. Horizontal synchronization signal H
sync indicates the start timing of each line of the image.

Since the memory control unit 53 writes the image signal DT into the buffer memory 55a or 55b according to the synchronization signal CTL, the input rate of the image signal DT may be any. The control unit 11 allows input of image data of various rates, and expands its application range. The input rate of the image signal DT is not limited to 60 frames / s, and may be 1 frame / s or a still image.

The memory controller 53 periodically reads out the image signal from the buffer memory 55a or 55b via the output switch 56, and outputs the image signal at a constant rate.
Supply to By periodically reading the image signal at a predetermined cycle, the rate of the image signal can be converted. The readout rate is the rate of the converted color image signal,
For example, it is 30 to 100 frames / s, preferably 60 frames / s.

For example, the image signal DT of the first frame is written into the buffer memory 55a, the image signal DT of the second frame is written into the buffer memory 55b, and the image signal DT of the third frame is then written. The data is written to the buffer memory 55a.

At this time, from the time when the image signal DT of the first frame is written to the time when the image signal DT of the second frame is written, the same first image data is periodically transferred from the buffer memory 55a at, for example, 60 frames / s. The image signal of the frame is read.

Next, from the time when the image signal DT of the second frame is written to the time when the image signal DT of the third frame is written, the same second frame image is periodically transferred from the buffer memory 55b at, for example, 60 frames / s. The image signal of the frame is read.

The output switch 56 is connected to the buffer memory 55
When the writing to a is completed, the output from the buffer memory 55a is selected, and when the writing to the buffer memory 55b is completed, the output from the buffer memory 55b is selected.

The image signal processor 57 converts the Y / C signal into an R signal.
/ G / B signal. However, the image signal supplied from the buffer memory 55a or 55b is R / G / B
If it is a signal, there is no need to perform this conversion. Next, the R / G / B signal is output to the look-up table 58 at a time division of 90 to 300 frames / s. Preferably 18
Output at 0 frames / s.

The look-up table 58 has R / G / B
The gradation conversion of each pixel value of the signal is performed. The lookup table 58 stores the pixel value before conversion and the pixel value after conversion in association with each other, and stores an R value for realizing the characteristic shown in FIG.
/ G / B image signal ILCD is output to the liquid crystal display. Tone conversion may be performed using a predetermined function expression instead of the lookup table 58.

The number of pixels of the image signal DT input to the buffer memories 55a and 55b is not fixed. When the size of the liquid crystal display is 320 × 240 pixels, 320 × 24
In addition to 0 pixels, an image signal DT of 640 × 480 pixels can be input to the buffer memory 55a or 55b.

In this case, the number of pixels of the image signal DT is supplied to the command decoder 51 as the control command CMD.
The command decoder 51 recognizes the number of pixels of the image signal DT and instructs the memory control unit 53 to convert the number of pixels of the image signal. In the above case, the image can be converted from an image of 640 × 480 pixels to an image of 320 × 240 pixels by thinning out the image by に つ い て in the vertical and horizontal directions. Specifically, the number of pixels can be reduced by the memory control unit 53 decimating and writing the image signal DT in the buffer memory 55a or 55b.

The conversion of the number of pixels may be performed by another method. The memory control unit 53 does not skip the image signal DT
May be written into the buffer memory 55a or 55b, and the image signal may be thinned out from the buffer memory 55a or 55b and read out to reduce the number of pixels. Also,
The image signal processing unit 57 may perform pixel number conversion by thinning or interpolation.

As described above, the input rate of the input image signal DT is free, and the image signal DT may be input irregularly. When the memory control unit 53 detects that the image signals DT input to the buffer memories 55a and 55b are still images, the memory control unit 53 outputs a signal SLP,
Stop the operation of all or a part of the video source. When the operation of all or part of the video source is stopped, the image signal DT is not supplied to the control unit 11, but the power consumption can be reduced. Thereafter, the memory control unit 53 continues to periodically read the image signal of the same frame from the buffer memory 55a or 55b. A still image is displayed on the liquid crystal display.

Next, the drive signal generator 52 will be described. The drive signal generator 52 responds to the synchronization signal CTL
A driving signal SLCD for the liquid crystal display and a lighting signal SLED for the light emitting diode are output. Drive signal SL for liquid crystal display
The CD is a signal for displaying the image signal ILCD on the liquid crystal display by raster scanning. The lighting signal SLED of the light emitting diode is shown in FIG. 2 and is a signal for sequentially lighting the red, green and blue light emitting diodes.

As described above with reference to FIG. 2, the relative timing between the lighting signal SLED supplied to the light emitting diode and the image signal ILCD supplied to the liquid crystal display is important. It is desirable that this timing is actually determined by human subjective evaluation. The control unit 11 can adjust the timing of the lighting signal SLED. The method will be described below.

The timing of the lighting signal SLED is supplied to the command decoder 51 as a control command CMD. The command decoder 51 determines the timing of the lighting signal SLED in response to the control command CMD.
Instruct 2 The drive signal generator 52 generates a light-emitting diode lighting signal SLE in accordance with the instructed timing.
D is output. In the lighting signal SLED shown in FIG.
The red lighting signal 32R, the green lighting signal 32G, and the blue lighting signal 32B can be shifted by the same time.

FIG. 6 is a configuration diagram in which the image display device shown in FIG. 1 is applied to a reproduction-only device. The reproduction-only device reproduces and displays an image signal recorded on a recording medium.

The recording medium 61 is, for example, a flash memory, and is a JPEG (joint photographic experts g).
roup) The image signal compressed by the method is stored. JPEG
The compression method is one of the standard compression methods for still images.

The microprocessor (MPU) 62 controls the entire reproduction-only device, and mainly controls the recording medium 61 and the digital signal processor (DSP) 63. The MPU 62 reads out the compressed image signal from the recording medium 61 and supplies it to the DSP 63. The DSP 63 expands the compressed image signal by the JPEG method, and writes the expanded image signal in the DRAM 64.
The DRAM 64 is a frame memory and has a storage capacity for one frame of image signal. DSP 63 is DRA
The image signal in M64 is read and supplied to the control IC 66.

The clock generator 65 is, for example, 25 MHz
Of the DSP 63 and the control IC 66
To supply. The DSP 63 and the control IC 66 operate according to the clock signal generated by the clock generator 65.

The control IC 66 corresponds to the control section 11 shown in FIG. 5, and performs rate conversion of an image signal, conversion of the number of pixels of an image, gradation conversion, and the like. The control IC 66 has a control signal SLC
D is supplied to a liquid crystal display (LCD) 68 and an image signal IL
The CD is supplied to the D / A converter 67, and the lighting signal SLED is supplied to the driver 69.

The D / A converter 67 converts the image signal ILCD from a digital format to an analog format,
8 The liquid crystal display 68 corresponds to the liquid crystal display 7 in FIG. 1A, and is driven according to the analog image signal and the control signal SLCD.

The driver 69 drives the light emitting diode (LED) 70 according to the lighting signal SLED. The light-emitting diode 70 corresponds to the light-emitting diode 10 of FIG. 1A, has three color light-emitting diodes, and emits light in accordance with the lighting signal SLED.

FIG. 7 is a configuration diagram in which the image display device shown in FIG. 1 is applied to a digital still camera. A digital still camera can capture a still image and record the still image in a flash memory.

The solid-state image pickup device (CCD) 71 has a photodiode (photoelectric conversion device) and a charge-coupled device (charge transfer path), generates an image signal according to the received light, and generates an analog signal processor (ASP). 72.
The solid-state imaging device 71 has, for example, a color filter of a Bayer array, and generates a color image signal of, for example, 60 frames / s. The image signal to be generated may be an interlaced system or a non-interlaced system.

Digital signal processor (DSP) 6
3 operates on a 3.3V power supply. The driver 73 is a DS
3.3V supplied from P73 is converted to 5V and supplied to the solid-state imaging device 71. The solid-state imaging device 71 operates with a 5V power supply.

The ASP 72 performs analog signal processing on an image signal received from the solid-state image sensor 71. Specifically, amplification is performed by a correlated double sampling (CDS) amplifier, white balance is performed by gain adjustment for each color, and an image signal is converted from an analog format to a digital format and supplied to the DSP 63.

The microprocessor (MPU) 62 controls the entire digital still camera, inputs operation information of the operation element 74, and mainly controls the DSP 63 and the flash memory 61. The operation element 74 has a power switch, a recording button (shutter button), a reproduction button, and the like that can be operated by the user.

The DSP 63 performs digital signal processing on the image signal received from the ASP 72. Specifically, the input image signal is written into the DRAM 64. Next, since only one color of the image signal exists in each pixel, an image signal of three colors is generated for each pixel by interpolation processing. Next, the image signal is converted from the R / G / B signal to the Y / C signal,
Write to 64. Next, saturation enhancement and outline enhancement are performed.

The DSP 63 supplies the Y / C image signal in the DRAM 64 to the control IC 66. The DSP 63 and the control IC 66 operate at 25 MHz generated by the clock generator 65.
It operates according to the clock signal of. Specifically, control I
The C66 receives an image signal according to a 25 MHz clock signal generated by the clock generator 65 and outputs an image signal according to a 20 MHz clock signal generated by the clock generator 75.

When the recording button (shutter button) on the operation element 74 is pressed, the DSP 63
JPEG compression of the / C image signal. The MPU 62 writes the compressed image signal into the flash memory 61.

When the play button on the operation element 74 is pressed,
The MPU 62 reads out the compressed image signal from the flash memory 61 and supplies it to the DSP 63. The DSP 63 expands the compressed image signal by JPEG, and converts the expanded image signal into a DR.
Write to AM64. Next, the DSP 63
4 is supplied to the control IC 66.

The operations of the control IC 66, the D / A converter 67, the liquid crystal display 68, the driver 69, and the light emitting diode 70 are the same as those described with reference to FIG.

The DSP 63 converts the moving image received from the solid-state imaging device 71 via the ASP 72 into a control IC 6 in real time.
6 or by expanding a compressed image signal in the flash memory 61 to supply a still image to the control IC 66.

When the control IC 66 determines that the input image signal is a still image, the control IC 66 outputs the signal SLP to the DSP 6
Output to 3. When detecting that the image generated by the solid-state imaging device 71 does not change for 5 seconds or more, the control IC 66 may determine that the image is a still image. Alternatively, a VD signal or a Vsync signal corresponding to a start signal of one screen of an image may be checked, and if the VD signal or the Vsync signal has been stopped for one screen time or more, it may be determined that the image is a still image. When receiving the signal SLP, the DSP 63 stops its operation and enters the energy saving mode. Not only DSP63,
The operations of the solid-state imaging device 71 and the ASP 72 may be stopped.

When the operation of the DSP 63, the solid-state image sensor 71, and / or the ASP 72 stops, the control IC 66 continues to output a still image in the internal buffer memory at a predetermined rate. A still image is displayed by the liquid crystal display 68 and the light emitting diode 70.

When the user operates the operating element 74, the DSP 63, the solid-state image sensor 71 and / or the
2 can be put into operation again.

The solid-state image sensor 71 has a size of 320 × 24
A pixel having various numbers of pixels such as 0 pixels, 640 × 480 pixels, or 1280 × 960 pixels can be used. Control I
When the C66 thins out the image signal, an image having a predetermined number of pixels can be displayed on the liquid crystal display 68.
The solid-state imaging device 71 includes a photoelectric conversion device such as a photodiode or a photocapacitance. As the solid-state imaging device 71, a CMOS having a photoelectric conversion device is used.
A sensor or a MOS sensor may be used.

FIG. 8 shows the image display device shown in FIG.
It is a block diagram applied to the C (national television system committee) monitor. The NTSC monitor displays an image based on the NTSC image signal. The NTSC signal is a signal of a television system adopted in Japan, and its application range is wide.

The video tape 81 records an image signal photographed by a video camera and a television program recorded by a video deck. The video decoder 82 reads an image signal from the video tape 81, reproduces an NTSC composite image signal, and supplies the reproduced NTSC composite image signal to the Y / C separator 83. Y / C
The separator 83 may receive an NTSC composite signal from a television antenna or the like in addition to the video decoder 82. The NTSC composite signal is a 60 field / s interlace signal in which a luminance (Y) signal and a chroma (C) signal are combined.

The Y / C separator 83 has an A / D converter, separates the NTSC composite signal into a luminance signal and a chroma signal, and converts the luminance signal and the chroma signal from an analog format to a digital format. The oscillator (OSC) 84 has two
A 4.54 MHz clock signal is generated and supplied to the Y / C separator 83. The Y / C separator 83 outputs a 9-bit luminance signal LUM, a 9-bit chroma signal CHR, and a pixel clock DAV to the video decoder 85. The Y / C separator 83 has a frequency of 24.54 MHz supplied from an oscillator 84.
12.27MHz of 1/2 frequency based on the clock signal of
Is generated.

Specifically, the Y / C separator 83 includes a 9-bit luminance (Y) signal LUM and a 9-bit red chroma (C)
r) Combination of signal CHR and 9-bit luminance (Y) signal LU
M and a set of 9-bit blue chroma (Cb) signals CHR are output alternately.

The video decoder 85 has a pixel clock DA
The image signal is divided into square pixel image signals based on V. That is, N
In the TSC system, the number of lines in the vertical direction is specified,
Since the number of pixels in the horizontal direction is not specified, the horizontal direction of the image signal is divided so that one pixel becomes a square. One frame has 640 (horizontal) × 480 (vertical) pixels, and one field has 640 (horizontal) × 240.
(Vertical direction) pixels. Next, from the Y / C signal, the R / G
/ B signal.

The video decoder 85 outputs the R / G / B signal, the horizontal blanking signal HBLK, and the vertical blanking signal VBLK to the control IC 66. The vertical blanking signal VBLK indicates the start timing of each frame of the image,
The horizontal blanking signal HBLK indicates the start timing of each line of the image.

Instead of the horizontal blanking signal HBLK and the vertical blanking signal VBLK, a horizontal synchronizing signal Hs
The sync and the vertical synchronization signal Vsync may be used.

The microprocessor (MPU) 86 has N
This is for controlling the entire TSC monitor, and mainly controls the video decoder 85 and the control IC 66.

The oscillator (OSC) 87 generates a 20 MHz clock signal and supplies it to the control IC 66. Control I
C66 operates according to a 20 MHz clock signal.

The control IC 66, the D / A converter 67, the liquid crystal display 68, the driver 69 and the light emitting diode 70 are basically the same as those described with reference to FIG.

The image signal of the interlaced system is supplied to the control IC 6
6 is input. The control IC 66 includes one field 640
X240 pixel image signal is thinned out only in the horizontal direction to obtain 32
An image signal of 0 × 240 pixels is generated. Control IC 66
Has first and second buffer memories 55a and 55b as shown in FIG. 5, writes a first field into the first buffer memory 55a, and writes a second field into the second buffer memory 55b. .

The control IC 66 performs rate conversion and gradation conversion, and outputs signals SLCD, ILCD, and SLED at a predetermined rate based on a 20 MHz clock signal generated by the oscillator 87. The image signal ILCD is 8 bits.

This embodiment can be applied to a video monitor capable of displaying other television signals such as the PAL system in addition to the NTSC system. In addition, the present embodiment can be applied to a head mounted display that displays an image by being mounted on a human head in a game or the like. In addition, the present embodiment can be applied to a PDA (personal digital assistant) which is a portable information terminal having a communication function and a pen input function.

The conventional backlight type liquid crystal display device is hard to see in a bright place such as outdoors, and the conventional reflective liquid crystal display device is hard to see in a dark place such as indoors. According to the present embodiment, as shown in FIG. 1, since the light-emitting diode 10 and the liquid crystal display 7 are provided in the finder portion 2 having the magnifying lens 5, external light can be blocked.
Since the image area occupies most of the user's effective visual field, the image is always easy to see without being affected by the surrounding brightness.

Further, by using the small liquid crystal display 7, the liquid crystal display 7 can be accommodated in the finder section 2. If the liquid crystal display 7 is optically enlarged by the magnifying lens 5, it becomes easier for the user to see. According to this embodiment, it is possible to provide a finder-type image display device in which a user can view an image by looking through the finder.

Further, the color liquid crystal display device according to the prior art has, for example, a color filter of a delta arrangement and each pixel is one color, so that a false color or coloring at an edge portion occurs. In this embodiment, since all the pixels have three color signals, it is possible to prevent false colors and coloring at edge portions. In addition, since it is not necessary to provide a color filter on the liquid crystal display, manufacturing of the liquid crystal display is simplified.

A conventional backlight type liquid crystal display device has a fluorescent lamp for backlight inside, but according to the present embodiment, a light emitting diode is used instead of the fluorescent lamp. Since the light emitting diode consumes less power than a fluorescent lamp, when the image display device is driven by a battery, the continuous operation time (battery life) of the image display device is relatively long. Further, since the light emitting diode is smaller than the fluorescent lamp, the size of the image display device can be reduced.

In the color liquid crystal display device according to the prior art, a color filter is provided in a portion corresponding to each pixel on the liquid crystal surface, and the color filter transmits only a wavelength of a predetermined color component and a wavelength of an unnecessary color component. The light use efficiency is poor. According to the present embodiment, since the coloring is performed by the originally required three colors of light emitting diodes without using a color filter in the liquid crystal display, light use efficiency is high. In other words, power consumption for obtaining image signals of the same luminance can be reduced.

By adjusting the control timing of the liquid crystal display and the control timing of the light emitting diode, the present embodiment can be applied to an experimental apparatus for physiological research, such as for examining response characteristics of human eyes.

Although the present invention has been described in connection with the preferred embodiments,
The present invention is not limited to these. For example, it will be apparent to those skilled in the art that various modifications, improvements, combinations, and the like can be made.

[0116]

As described above, according to the present invention,
In the liquid crystal display, all the pixels can transmit red, green and blue light, and the red, green and blue light emitting diodes illuminate the back of the liquid crystal display, so that all the pixels have three color components. However, it is possible to prevent false colors and coloring at edge portions.

A light emitting diode illuminates the back surface of the liquid crystal display. Since a light emitting diode consumes less power than a fluorescent lamp, when the image display device is driven by a battery, the continuous operable time (battery life) of the image display device can be relatively long.

Without providing a color filter on the liquid crystal display,
Since coloring is performed by light emitting diodes of three colors, light use efficiency is high. In other words, power consumption for obtaining image signals of the same luminance can be reduced.

[Brief description of the drawings]

FIG. 1A is a configuration diagram of an image display device according to an embodiment of the present invention, and FIG. 1B is a cross-sectional view of a liquid crystal display.

FIG. 2 is a timing chart of signals for controlling a liquid crystal display and a light emitting diode.

FIG. 3 is a flowchart illustrating a process of a control unit.

FIG. 4A is a graph showing voltage-transmittance characteristics without gradation conversion, and FIG. 4B is a graph showing voltage-transmittance characteristics after gradation conversion.

FIG. 5 is a block diagram illustrating an internal configuration of a control unit.

FIG. 6 is a block diagram showing a configuration of a reproduction-only device.

FIG. 7 is a block diagram illustrating a configuration of a digital still camera.

FIG. 8 is a block diagram illustrating a configuration of an NTSC monitor.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 image display device 2 finder unit 3 control circuit unit 4 user 5 lens 6, 8 polarizing plate 7 liquid crystal display 9 diffusion plate 10 light emitting diode 10 a red light emitting diode 10 b green light emitting diode 10 c blue light emitting diode 11 control unit 12 video source 13 power supply 21, 25 Transparent substrate 22, 24 Electrode 23 Liquid crystal 51 Command decoder 52 Drive signal generator 53 Memory controller 54 Input switch 55a, 55b Buffer memory 56 Output switch 57 Image signal processor 58 Lookup table 61 Recording media 62 Microprocessor 63 Digital signal processor 64 DRAM 65 Clock generator 66 Control IC 67 D / A converter 68 Liquid crystal display 69 Driver 70 Light emitting diode 71 Solid-state imaging device 72 Analog signal Processor 73 driver 74 operating element 75 clock generator 81 video tape 82 video decoder 83 Y / C separator 84 oscillator 85 video decoder 86 the microprocessor 87 oscillator ILCD image signal SLCD liquid crystal display control signals SLED light emitting diode control signal

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme court ゛ (Reference) G09G 3/20 611 G09G 3/20 611A 3/36 3/36 H04N 5/66 102 H04N 5/66 102B 9 / 30 9/30

Claims (10)

[Claims] 1. An image signal processing means for processing an image signal; an image signal output means for dividing the image signal processed by the image signal processing means into red, green and blue image signals and outputting them in a time-division manner; A liquid crystal display in which all the pixels can transmit red, green, and blue light, and changes the transmittance of each pixel in accordance with the red, green, and blue image signals output by the image signal output unit; A red, green, and blue light emitting diode capable of illuminating the back surface of the liquid crystal display; and causing the red light emitting diode to emit light in accordance with a timing at which the image signal output unit outputs a red image signal, and outputting the image signal. The green light emitting diode emits light in response to the timing at which the means outputs a green image signal, and the image light output means outputs the blue image signal in accordance with the timing. And a light emitting diode control means for causing the blue light emitting diode to emit light. 2. An image display apparatus according to claim 1, wherein said image signal processing means includes rate conversion means for outputting a moving image or still image signal inputted at an arbitrary rate at a constant rate. 3. The rate conversion means has two frame memories, and alternately writes an input image signal into the two frame memories in units of fields or frames. 3. The image display device according to claim 2, wherein an image signal is read out from the completed frame memory at a constant rate and output. 4. The image display device according to claim 1, wherein said image signal processing means includes RGB conversion means for converting a Y / C image signal into an R / G / B image signal. 5. The image display device according to claim 1, wherein said image signal processing means includes a gradation conversion means for converting a gradation of an input image signal according to a transmittance characteristic of said liquid crystal display. 6. The image display device according to claim 5, wherein said gradation conversion means has a look-up table for performing gradation conversion of an image signal. 7. The image display device according to claim 1, wherein said image signal processing means includes a pixel number conversion means for converting the number of pixels of an input image signal according to the number of pixels of said liquid crystal display. 8. The pixel number conversion means has a frame memory, and thins out input image signals and writes them to the frame memory, or writes input image signals to the frame memory and outputs the image signals from the frame memory. The image display device according to claim 7, wherein the number of pixels of the image signal is reduced by thinning out the signal and reading out the signal. 9. The light emitting diode control means according to claim 1, wherein a timing at which said light emitting diode emits light is shifted from a timing at which said image signal output means outputs an image signal in accordance with a timing adjustment signal. Image display device. 10. A finder having a lens for optically enlarging an image on the liquid crystal display, and housing the liquid crystal display and the red, green and blue light emitting diodes shielded from the outside. The image display device according to claim 1, further comprising: